1. Field of the Invention
The present invention relates to a tube cutting apparatus of the type used to sever lengths of tubing or other elongated stock continuously emanating from a fabrication mill.
2. Description of the Related Art
A typical tube cutting apparatus includes a cut-off die set operated by a ram. The die set is clamped to the tubing prior to the severing operation which is carried out by a vertically reciprocating cut-off or shearing blade. In cut-off systems of the double cut type after the die set is clamped to the tubing a notching blade is caused to move across and notch the upper periphery of the tubing prior to entry of the cut-off or shearing blade into the upper tube wall. Notching the tube in this manner reduces or eliminates dimpling or collapsing of the tube wall by the shearing blade, thus eliminating the need for reshaping the ends of the tubing after the cutting operation. Prior to notching the tubing, the tubing is typically clamped by a pair of opposed complemental die jaws which are mounted on reciprocally slidable mounting members having cam followers attached thereto. The cam followers engage a wedge cam which laterally displaces the cam followers and corresponding mounting members thereby closing the die jaws and clamping the die set to the tubing.
Once the tubing is clamped the notching blade is moved in a reciprocal manner across the upper periphery of the tubing by a cross slide. Both push and "pull across" notching methods are known. See for example U.S. Pat. Nos. 4,109,555 and 4,294,147. In order to translate the vertical reciprocal motion of the upper and lower platens into a horizontal reciprocal motion of the cross slide, a cam having a curvilinear cam track is mounted to the upper platen and a cam follower is fixed to the cross slide. As the ram of the cut-off press begins its downward stroke, the cam attached to the upper platen is also urged downward causing the cam follower to follow the curvilinear cam track. Movement of the cam follower causes movement of the cross slide which correspondingly drives the notching blade through the notching stroke. Once the tubing is severed, the press operating in a reverse manner raises the upper platen of the die set which causes the cam follower positioned in the curvilinear cam track to return the cross slide to its initial position in preparation for a new cutting cycle. Use of the cam/cam follower assembly in the manner set forth above allows the reciprocating vertical motion of the upper platen to be translated to a reciprocal horizontal motion of the cross slide. Cross slide assemblies of this type are known see U.S. Pat. No. 4,766,792.
Time is of the essence in the tube cutting industry, tubing continuously emanates from the tube mill at a high rate of speed. Thus any problems, delays or shut-downs for repair or replacement of the cutting equipment correspondingly results in a shut-down of the tubing mill resulting in loss production and revenue for the tube maker. A cut-off die set cycles at a high rate of speed, typically performing up to 60 cuts per minute. Therefore it is an object to simplify and reduce the size and weight of the die set components to reduce the inertial and frictional forces occurring during die set operation. Reducing the inertial and frictional forces and simplifying the operation of the die set reduces the potential for die set or component failure and increases the life of the die set. Increased die set life increases the period of time the mill is operational thereby increasing production and revenue for the tubemaker.